Raj Kumar Sanpui:-
When a crash occurs, the most important diagnostic data to obtain is the |process core file. To ensure that this file is generated, you must make the |settings described in the following sections.
| |Operating system settings
|Operating system settings must be correct. These settings can vary by distribution |and Linux version
|To obtain full core files, set the following ulimit options:
|ulimit -c unlimited

turn on corefiles with unlimited size|ulimit -n unlimited

allows an unlimited number of open file descriptors
|ulimit -u unlimited

sets the user memory limit to unlimited
|ulimit -f unlimited

sets the file limit to unlimited
|The current ulimit settings can be displayed using:
|ulimit -a
|These values are the "soft" limit, and are set for each user. These values |cannot exceed the "hard" limit value. To display and change the "hard" limits, |the same ulimit commands can be run using the additional -H flag. From Java 5, the ulimit -c value for the |soft limit is ignored and the hard limit value is used to help ensure generation |of the core file. You can disable core file generation by using the -Xdump:system:none command-line option

Ok, and you both (Raj and Jalal) realize you're talking about application cores, rather than system cores. That's not going to help in this instance.
And Raisul, you're talking about Solaris, not Red Hat. Again, not useful.
I'm not sure there is a mechanism for capturing system cores in Red Hat. I'm hunting for one myself.
-Ben.

Hi Jalal,
Thanks for the answer. May be I need to more specific what i need here. Is there any way that linux system generates automatic system crash dump in case of system hang.Found some ways of manual invocation by sysreq key but we need system to generate crashdump if it is hard hang.
Thanks
Faisal